In the classical understanding of Pranayama from the Patanjali Yoga Sutras, it is taught that Prana is the Life Force while Yama is the practice to control. Therefore, Pranayama can be understood as ‘to control the life force’.
The various techniques of breath excercises and regulatory methods performed by the Yogi can allow access to deep levels of healing, psychic expansions and vital energy which can both support the overall yogic practice (sadhana) as well as health and strength of the practitioner.
During the practice of Pranayama the stimulation of the system of Nadis in the body are activated, in time giving through experience perception realms beyond the physical such as, the emotional, the pain, the pranic and the bliss bodies. Eventually this leads the practitioners into a process both of self healing and spiritual advancement.
Several interpretations and understandings of what Pranayama is and does has been stated by advanced and realized Yogis as well as has been written in sacred texts of India. Some prominent examples of this come from the well known spiritual teacher Shankaracharya who expressed in his profound teachings on spiritual thought that the practice of pranayama is to retain nothing but the experience, thought and perception of Brahman (pure consciousness).
While in the sacred scripture The Gita, it has been written that there are two aspects to the breath which are; the outgoing (apana) and the incoming (prana). In this manner when these two parts merge together there is the experience of pure Brahman (pure consciousness). The discontinuance of inhalation and exhalation can be brought about by Kriya Yoga. Kriya Yoga can be learned only by a real Guru. Once the Yogi is ready to dive in higher form of Yoga practice, the Guru will appear (It can be any kind of Guru). This is a form of Pranayama, the gradual unforced cessation of breathing. There are different techniques of Kriya Yoga Pranayama, wherein the human blood is decarbonized and recharged with oxygen. The atoms of this extra oxygen are then transmuted into life current, rendering breathing unnecessary for certain periods. Through the practice we move from matter to spirit and increase our willpower. Our five senses, touch, taste, sight, smell and hearing are thus disconnected, and the attention is freed from any possible invasion of sensory perceptions. In deeper states of Pranayama practice we have than purified our mind, body and the nadis to such a degree that true meditation is accessed. Thus, the practitioner reaches a state of Brahman, which is beyond the mind, the ego, and duality.
Bhagavad Gita describes Kriya Yoga as highest form of spiritual practice, where the Yogi is neutralizing the breaths, realizes the life force from the heart and brings it under his/her control. Trying to control the life force by holding the breath in the lungs for uncomfortably long periods causes harmful pressure on the heart, lungs, diaphragm, and arteries, and should be therefore be strictly avoided.